1. Field of the Invention
This invention relates in general to a method and apparatus to provide an automatic depth and/or height control system, and more particularly to a method and apparatus to automatically control the depth or height position of an agricultural or other mobile tool using a hydraulic system.
2. Description of Related Art
This invention generally relates to the inventions disclosed within U.S. Pat. No. 4,646,620, and U.S. Pat. No. 4,825,655, which are both incorporated herein in their entirety, that relate to fluid cylinder systems and allow for control of piston stroke positions.
Historically, the depth of tool penetration for agricultural equipment, or other soil penetration equipment, has been set by mechanical devices which restrict the retraction or extension of hydraulic cylinders. The cylinder(s) is typically mounted between the frame of the implement and the leg of an implement carrier wheel. Thus, height of the frame above the ground, which determines tool penetration, could be hydraulically changed to a more shallow depth (ie., less tool penetration) but not to a deeper depth typically because of mechanical restriction. The prior approach is still in use but does not offer good control of material discharge, liquid manure deposits, preparation tillage, ground cover, moisture retention, seed bed preparation or depth of seeding. The prior approach is less desirable because on hard ground the wheels ride up onto the surface, the tools are not set deeper, and this results in shallow tool penetration. On soft ground where the wheels ride deeper, hydraulic corrections can be made with use of manual hydraulics, but fine adjustments are difficult and continuous.
Similar issues also exist within similar mobile tools such as sprayer booms, road side grass mowers, and other earth moving, working or discharging equipment. In these other applications, both tool height and depth above the ground is to be controlled. The height and depth measurement for the tool as well as the control system used to the height and depth of these tools are improved by the present invention.
Recently, automatic depth control systems have been brought onto the market which control the extension and retraction of the implement carrier cylinders in order to hold a select depth. One such system is disclosed within U.S. Pat. No. 4,646,620. Automatic depth control is controlled by a microprocessor in the tractor cab, sensors on the implement frame and power beyond valving for hydraulic corrections to maintain a given tool penetration. Sensors for this system were depth gauge wheels.
Another such system sold by Raven Industries of Sioux Fall, S. Dak., has a rotary dial on the console to set the working depth. It is difficult to change depth settings on-the-go since selective depths are not programmed. Sensors are Piezo ultrasonic. Power beyond valving requires one of three separate and distinct manifold assembles, either gear pump, pressure compensated or load sensing. This requirement for three separate and distinct valving manifolds for different tractor hydraulic systems is costly; also, the valving is in-line but cannot accommodate manual return flows. Thus, changes from automatic to manual or vice versa require a hoses to be reconfigured.
Thus, there is a need for a more efficient system that is more adaptable to on-the-go farming practices and offers better control of depths for operations on varying soil textures (sand, silt and clay), weather affect upon these soils, and control for various implements, applications, and field conditions.